Bodhisattva

"Buddhism asserts that the path of the bodhisattva is not an otherworldly undertaking for people with unique gifts of compassion or wisdom. Rather, the life-condition of bodhisattva is inherent in the lives of ordinary men and women, and the purpose of Buddhist practice is to strengthen that state until compassion becomes the basis of all our actions."
A bodhisattva is literally a living being (sattva) who aspires to enlightenment (bodhi) and carries out altruistic practices. The bodhisattva ideal is central to the Mahayana Buddhist tradition as the individual who seeks enlightenment both for him- or herself and for others. Compassion, an empathetic sharing of the sufferings of others, is the bodhisattva's greatest characteristic. It is shown in the following incident from the Vimalakirti Sutra which concerns a prominent lay follower of the Buddha who had fallen ill. When questioned about his illness, Vimalakirti replied, "Because the beings are ill, the bodhisattva is ill. The sickness of the bodhisattva arises from his great compassion."
It is held that the bodhisattva makes four vows expressing a determination to work for the happiness of others: "However innumerable sentient beings are, I vow to save them; however inexhaustible the passions are, I vow to master them; however limitless the teachings are, I vow to study them; however infinite the Buddha-truth is, I vow to attain it."
The vows, each of which commits the bodhisattva to the open-ended pursuit of a continually receding goal, may seem daunting. Buddhism asserts, however, that the path of the bodhisattva is not an otherworldly undertaking for people with unique gifts of compassion or wisdom. Rather, the life-condition of bodhisattva is inherent in the lives of ordinary men and women, and the purpose of Buddhist practice is to strengthen that state until compassion becomes the basis of all our actions.
In addition to compassion, the vows reflect the bodhisattva's commitment to self-mastery, to study and learning, to the attainment of wisdom. None of these, however, is pursued in a vacuum, merely to improve or adorn the self; at the base of all these efforts is always the determination to remove the sufferings of others, and to replace them with joy.
For the followers of Nichiren Buddhism, bodhisattva practice is subsumed in the twin, mutually reinforcing aspects of "practice for oneself and others." The core of practicing for oneself is the recitation of Nam-myoho-renge-kyo (the "daimoku" of the Lotus Sutra) along with key passages from the sutra. The purpose of this practice is to revolutionize one's inner life, to develop the qualities of the Buddha: courage, wisdom, compassion and abundant vitality or life-force.
While many people may at first be inspired to practice Buddhism by the desire for personal happiness, to overcome illness or some other seemingly insurmountable challenge, as their life-state expands, they naturally develop a deeper concern for the happiness of others. Perceiving the interconnectedness of all beings, they take compassionate action, including sharing with others the insights of Buddhism, so they may also tap into the same rich inner resources that lie within their lives.
Bodhisattvas are thus naturally engaged in society, actively struggling both to change themselves and make the world a better, more humane place for all people. This explains why members of the SGI strive to be valuable participants in society, and to contribute as much as possible to their family, workplace and community.

Source: http://www.sgi.org/buddhism/buddhist-concepts/bodhisattva.html